


Trial and Error

by LittleQuail



Category: Undertale (Video Game)
Genre: Asphyxiation, Darkness, Dirty Talk, Drug-Induced Sex, Gender-neutral Reader, Other, Sans is Gaster's assistant, Tentacles, Vibrators, after that its all porn, first chapter is all plot
Language: English
Status: In-Progress
Published: 2015-12-14
Updated: 2016-05-24
Packaged: 2018-05-06 15:26:50
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 6
Words: 6,785
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5422187
Author URL: https://archiveofourown.org/users/LittleQuail/pseuds/LittleQuail
Summary: <blockquote class="userstuff">
              <p>Mt. Ebott was supposed to be your ticket out. A quick ending. Painless, just the rush of air, then nothing. </p>
<p>That wasn’t what had happened at all.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> So, sorry if this chapter is kind of boring, but I needed to get everything established before moving on to the actual fun. Thanks for reading!

Mt. Ebott was supposed to be your ticket out. A quick ending. Painless, just the rush of air, then nothing. 

That wasn’t what had happened at all.

You had landed in a pile of bright gold flowers, met one that talked, and was saved by a talking goat. Already, this was weirder than you had thought death was supposed to be. It wasn’t until you had ‘fought’ Toriel and went outside into the snow that you started to worry. It was cold, and you went straight up to a gate with posts farther apart than necessary. A tall skeleton stepped out from the woods behind it, looking triumphant with his hands on his hips.

“I’VE GOT YOU NOW, HUMAN! YOU’RE TRAPPED! THERE’S NO WAY YOU COULD GET THROUGH TH-” You walked through the bars, stopping him in his tracks. “OH. WELL, NEVERMIND! I WILL CAPTURE YOU MYSELF!” You felt fear run down your back and you ran past him, huffing as you could hear him coming after you. “STOP! CEASE! I WILL GET YOU!” 

You looked back to see how close he was to you, and in doing so, ran straight into a tree. You fell to the ground on your back, crunching the snow beneath you. You groaned and blinked your eyes open again, as they had closed when you fell. The skeleton was right above your face. 

“LOOKS LIKE YOU’LL HAVE TO GIVE UP TO ME NOW! COME ON HUMAN, LET’S GO.” With that, he took your wrists and pulled you up, popping both of them with the force. You yelped and he let go. “OH, SORRY, I FORGOT HOW FRAGILE YOU HUMANS ARE. WE HAVEN’T HAD ONE IN A WHILE.” Instead, he grabbed your arms and dragged you along behind him, you going along reluctantly. You looked around, trying to find something that would get you out of this, but the deserted snow and forests surrounding you seemed hopeless. 

He took you to his house, where he locked you in his shed while he went to go get his ‘superior’. It seemed like hours had passed before he opened up the door again, but this time, with a woman in armor standing beside him. 

“So, this is the runt? Can’t believe you actually caught them, Papy. Good job. Maybe I’ll let you into the Royal Guard after all.” The woman said, crossing her arms and smirking as she got closer to you. Papyrus smiled, his eyes aglow.

“DO YOU REALLY MEAN THAT, UNDYNE? OH, WHAT A FANTASTIC DAY! I’LL HAVE TO GO TELL MY BROTHER!” He left the two of you alone as he nearly skipped to the house next door. Undyne stepped closer to you, the half-smile never leaving her face. 

“You must be really stupid to get yourself caught by Papyrus. I know just the place to take you.” She grabbed your wrists, which were still painful from earlier, and led you out. 

~*~

It took forever, with so many twists and turns, people asking questions and glaring at you for no good reason. 

You ended up in a large white examination room, strapped down to a table with bands around your wrists, ankles, and one around your waist. It felt more like a hospital than anything else. One where anything could happen, from torture to dissection to everything in between. You had been left there for at least a couple hours now, your stomach starting to rumble with hunger, and your head swimming from the bright lights. 

Finally, the door swung open, revealing a tall skeleton with a lab coat and a black turtleneck, and a smaller skeleton with a similar looking lab coat and a simple t-shirt on. They were both carrying clipboards.

“Good evening, my name is Dr. W. D. Gaster, and this is my assistant, Sans. I’m sure you’re very frightened, but don’t be - we’re here to simply study,” the one named Gaster said. “For now, we just want to take some samples of you. Sans, if you would, please.” The smaller one went behind your table and pulled out a small cart full of vials. He filled one with a couple pieces of your hair, another with your spit, and one last one with your blood. 

“That’s all we’ll need. Someone will be in to bring you food some time soon, and we’ll be back by the end of the day.” Gaster nodded and Sans took the vials with him as the two left the room. 

You sighed. This was not what you expected when you jumped down that hole in the mountain.


	2. Chapter 2

**Summary for the Chapter:**

> Experiment 1: Drug-induced sex.

**Notes for the Chapter:**

> guh ive got it bad, man. this will end up being many chapters with different kinks in each one. Thanks for reading!

Days later, you were getting accustomed to the routine of eating, taking vitals and samples, eating again, then sleeping. It was boring, sure, but at least it wasn’t torture. That’s what you were thinking when Gaster and Sans came in with a cart full of vials and needles, different than the ones used for blood samples. 

“Today is a.. special day, for both you and for us. We’ve been developing something that we think will help us in our development of artificial determination, and we think we’ve got it down,” Gaster explained. “Sans, go ahead and inject it.” 

You squirmed around on the table, the binds keeping you from moving too much. The smaller skeleton grabbed your forearm and injected in a bright purple liquid into your vein. It felt like fire was rushing through you, before settling in-between your legs. This simply made you wriggle more, trying to rub your legs together and create friction. 

“Tell us what you feel, if anything. Though, it seems like.. Are you in pain?” Gaster’s face grew quizzical, moving closer to you. He pressed a single digit onto your crotch, making you thrust your hips up in response. You shook your head no. 

“N-no! Something’s.. wr-wrong.” You were surprised you could even get that out, with how turned on you were - it was almost painful. He rubbed his finger on your pants, causing you to groan quietly. You wished you could move your hands to cover your mouth - doing this in front of your captors felt wrong.

Gaster hummed in curiosity. “If it’s not painful then - oh. Oh! I see. This is interesting, what a development! Sans, take notes if you could, I’m going to try something.” Sans nodded and clicked his pen, at the ready. 

Gaster moved his hand away from your warmth and hit a switch underneath the table. It caused you to move lower and in a perfectly flat position. He ran a hand down your side, causing you to jump a little, before he made his way back down to your heat. He slid a finger from top to bottom, making you moan and move your hips up. 

“Fascinating. It seems instead of taking determination, we’ve made.. An aphrodisiac. Well. That’s not what we had intended at all.” He reached up and unbuttoned your pants, zipping them down to reveal your underwear. “Let’s see how potent it is.”

You lifted your butt off the table to help him take off your pants, letting out a small yelp as the cold table hit your legs. He laid your pants to the side, folding them neatly. His whole palm found its way to your crotch once more, rubbing and sliding up and down, making you squirm all over. 

“Simply putting pressure on the experiment causes them to move in ways I’ve never seen before. I’m going to continue to investigate,” Gaster dictated. He slid down your underwear and looked at you with clinical seriousness. “Experiment is fully.. Turned on, I suppose. The substance is in full effect now.” He continued to press down on you, rubbing you, until he slid one finger down to your hole. He slowly pressed one knuckle in, his eyebrows springing up in surprise. “The experiment is.. Tight. And very, very warm. Maybe if I..” He pressed more of his digit in, causing you to press your hips down onto him, his whole finger going in. He curled his finger and you let out a gasp, then a moan as your sensitive spot was hit inside of you. “Interesting.” 

He continued this motion, causing you to spasm against the restraints. “Please, please Gaster, m-more-” your eyes flew wide open as you realized what you said. Both Sans and Gaster looked at you in shock, the older skeleton stopping his movements. 

“...This is an interesting turn of events. Sans, write that down.” Sans hesitated, scribbling down what you had said quickly. The doctor pressed his finger fully in once more, now reveling in your stifled moans. “Please, don’t be quiet for us, we need to know everything that you want or feel.”

You took his command to heart and moaned loudly as he hit your spot again, now a moaning mess. He pushed in another finger and let out a small noise himself, his cheeks glowing a dark grey in blush. Once you were accustomed to two fingers, a third joined in and soon you could tell you were close. 

“I-I can’t.. take it much l-longer.. G-Gaster I-I’m gonn-a-ah!!” You tightened around his fingers, his digits that were still pumping, drawing out your orgasm. You let out a loud moan as waves upon waves of your climax hit you. It wasn’t until it had stopped completely that Gaster drew his fingers out, wiping off your fluids into a small container on the cart. 

“That was.. A captivating experiment, to say the least. Sans, do you agree?” The taller skeleton was trying to compose himself, straightening his lab coat and trying to get the blush off of his face.

“It was certainly stimulating, that’s for sure.” Sans gave a small smile, trying not to laugh at his own pun. Gaster gave a sigh, also trying not to laugh. You were simply too tired to even try. 

Underwear and pants were put back on, a pat on the shoulder was given, and the two promised they’d be back soon with another experiment. You were just happy that the whatever-it-was that they gave you was wearing off, making you exhausted.

**Notes for the Chapter:**

> wanna know when im updating? follow my tumblr: thatssoquailmeat


	3. Chapter 3

**Summary for the Chapter:**

> Experiment 2: Vibrators and dirty talk.

**Notes for the Chapter:**

> this is. this is something. hope you like it! Thanks for reading!

After your little experience with the last substance they injected into you, you weren’t exactly looking forward to the next time. So when the door opened and Sans and Gaster came in, rolling a table of tools underneath a piece of fabric behind them, you were scared to say the least. 

“Since our last encounter, we’ve been developing some.. ideas about humans. We’re going to test them to see if they’re true.” With that, he pulled the sheet off, revealing some strange looking devices in all sorts of sizes and shapes. “We believe that humans have.. Well, we’re not quite sure what it is, if it’s an organ or simply a spot, but it’s somewhere inside of them that releases endorphins and, perhaps, determination. We’d like to find it, and these should aid us in our search.” 

Gaster picked up one that was, to be honest, more familiar to you than you’d like. It looked almost identical to a vibrator that you owned back home. It was slightly curved to hit that spot that made you jump, the spot you were certain they were looking for. The other devices you didn’t recognize, but thought they were for the same thing. The one that looked like a tongue sent a shiver down your back.

“First, we’d like to stimulate you, simply to get things, uh, started.” Gaster’s face got a light blush of grey on it, trying to keep his embarrassment about the whole thing to himself. He pressed a button on the end of the device and it turned on, the sound of the vibrator ringing through the room. He pushed the tip of it to your crotch over your pants, making you pull back away from it for a second in surprise. You relaxed, letting a moan slip past your lips at the sensation. Sans began scribbling down something on his clipboard. 

“Now that the experiment is ready, we shall begin the real trial.” The doctor took away the vibrator and turned it off before setting it down on the cart. He slipped your pants down, making a small noise as he noticed your underwear. “Experiment is.. Definitely ready.” He peeled those off next, a cold breeze going over your crotch, simply turning you on further. Gaster brought the vibrator back to you, turning it on once it was in contact. Your hips moved on their own, bringing yourself closer to it. 

“Experiment is responding positively to initial touch. Next, let’s try..” He moved the tip towards your hole, slowly pushing it in. You let out a groan, the pain turning into pleasure as it went all the way inside of you. It was big and long, larger than you had ever had before, and it stretched you in a way that sent a shock up your spine. You let out a gasp that turned into a moan as you felt the base hit your flesh. It filled you up and the vibrations went all through you. It wasn’t until Gaster pulled some of it out and thrusted it back into you, however, that you started moaning almost constantly, your tongue lolling out of your mouth. 

“Device one seems to hit the area as well as stimulate others. Device two will determine the actual spot. At least we know for certain there is something there.” He pulled out the vibrator, leaving you empty and painfully turned on. You squirmed, trying to find friction from something as he prepared the other object. Sans noticed.

“Hey, Doc, look at the experiment. Heh. They were really enjoying that.” He wrote a couple things down, Gaster swiveling his head around and raising his eyebrows in surprise. “I.. I suppose so. Those noises certainly weren’t nothing.” He turned back to his preparing, leaving you fidgeting on the table.

“Please.. Please, one of you, I n-need..!” You were ashamed of yourself for being so lewd, but you were definitely in need.

“Need what, experiment?” Sans smiled knowingly, taking a step closer to you. 

“I-I need.. I need more, more inside of me, please, put another one in, please..!” You strained against your binds, Sans chuckling. 

“You’re dirty, you know that?” Gaster spun around quickly, blush nearly overtaking his face now.

“S-Sans! That’s not appropriate! I-” You were leaking onto the table with your precum, your heartbeat beating through your heat. 

“Please, Gaster, Sans, put another one in, I need it, please! I’m so dirty, I’m such a slut, please!” You were begging at this point, your own warmth driving you nuts. Gaster cleared his throat and fumbled with his hands. 

Sans rolled his eyes and headed over to the cart, grabbing the next device. It ended up being the one shaped like a tongue and you raised your hips up, getting ready for it. Sans gave his clipboard to the still stunned scientist and pressed one of his bony fingers to your tight hole, enjoying the sounds you made. He removed it and replaced it with the tongue, pressing a button to make it vibrate. 

You let out a long, high moan, savoring the feeling of the bumps and ridges hitting you in all the right places. Sans pressed the tip of it up, hitting you right in your spot, causing your back to arch and your toes to curl. Gaster wrote furiously on the clipboard, excited he found something in this trial. Sans, on the other hand, was relishing your noises. He twisted the vibrator and found your spot again, making you tighten and gasp. 

He kept finding it, over and over, he was almost massaging it and eventually it got to you.

“Please, I-I’m so close, more, more!” You moved your hips in sync with Sans’ motions, trying to get more. 

“You’re such a dirty slut, you know that? Begging for release like this, pathetic slut.” Sans was enjoying this, he couldn’t hide it any longer. The noises you were making were making him hard, his boner pressing against his pants. Gaster was turned on too, but he was trying to hide his member behind a hand. 

“I’m such a slut, I’m go-onn-a-ah!!” A cord broke within you and you came, your juices getting all over the device and the toy, a little getting on Sans’ hand. You twitched as you rode out your orgasm, the vibrating device bringing more out of you. Gaster wrote down everything, trying to keep unflustered and scientific. Sans, on the other hand, was getting into it. 

“That’s it, you liked that, didn’t you? You like us watching you. Pervert.” He grinned, drawing the device out of you. You groaned as you felt empty, panting from your coming. He turned off the vibrator and placed it on the cart. “Gaster? I think the experiment is done for today.”

Gasters cheeks were fully flushed, his legs shaking. “R-right! Y-yes, I-I think we have all that we n-need for today. U-uh we.. We will be back w-when we have more t-to try out” He looked like he was about to pass out, and he left quickly, taking the cart with him but leaving Sans. The smaller skeleton just chuckled and redressed you before leaving as well.

**Notes for the Chapter:**

> want to suggest a kink? leave a comment or send me an ask at my tumblr: thatssoquailmeat !


	4. Chapter 4

**Summary for the Chapter:**

> Experiment ?: Darkness and Dirty Talk

**Notes for the Chapter:**

> i love writing porn right next to my parents :) Thanks for reading!

Dark.

The technicians turned the lights off at night to let you sleep. It was the only way you were aware time was passing. Your neck cramped every night from sleeping on it at an odd angle, but you were just happy to sleep.

You were dead asleep one night, dreaming of your old friends and family, until a noise awakened you. It was the door squeaking open slowly, and you blinked your eyes as you woke up. It was still dark, nobody should be here. You heard the door click shut again. With absolutely no light leaking in from anywhere, you couldn’t tell if someone had come in or if someone simply opened and shut the door. You hoped it was the latter.

You waited a moment, but upon hearing no movement, you closed your eyes again and tried to nod off. 

Something touched your arm. A chuckle rang out through the room. Your eyes shot open and you could feel the shot of adrenaline go through you. 

“Heh. You were really getting into our trial earlier today, weren’t ya?” You could tell immediately who was in the room with you and his voice sent shivers down your spine. 

“Sans, what are you doing here?” It came out as a whisper, as it seemed appropriate for the darkness. 

“To conduct a trial of my own, babe.” A switch was hit underneath the table, making it flat. A clatter, and then pressure on your legs and a warm breath by your ear. 

“I’m gonna make you squirm and scream more than that old coot did. It’s a good thing you’re tied down to this table ‘cause you won’t be able to walk when I’m done with you.” He slid a hand down your side, stopping to flick your sensitive nipples and getting a small gasp out of you. It continued down, cupping your warmth and pressing his digits against everything. You twitched under his touch and moaned quietly.

“Mmm heheh.. You’re already so turned on. So warm.. You’re just aching for this, aren’t you?” You nodded, but then realized he couldn’t see you, so a quiet “Yes, please” leaked out, making him chuckle once more.

In one swift move, he yanked down your pants and your underwear, leaving your bottom naked as he straddled your lap. He tossed the clothing items to the side, then shifted, and the next thing you felt was his bony hands on one of your ankles. 

“For this experiment, we’re gonna need these things off. Don’t try and run away now.” You could almost hear the smirk in his voice, his hands making quick work of your binds. He left the others on your wrists on. 

He picked up your hips and something wet touched your entrance. It slid over your heat and poked at your hole. You realized it was Sans’ cock and it pushed into you, slowly at first, then all at once until you could feel his bony hips against your ass. You let out a strangled yelp at the pain, but it turned into a moan as it melted into pleasure. 

“You ready for this, babycakes?” His voice was right next to your ear and it took all you had not to flinch away in surprise. 

“Y-yes” you squeaked out. 

“That’s not good enough. Tell me how bad you want me.” He moved not even an inch and you curled your toes in need. 

“Please, Sans, I want you, I wanna be fucked so hard by your cock, please, I need you!” You almost couldn’t believe yourself, but his dick inside of you felt so good, you didn’t care. You could feel him smirk as he kissed your neck. 

“Good.” He pulled out to his head, then thrusted in, making you see stars for a second. His cock violated you, every ram hitting your spot inside of you. You gasped, over and over, as he ravaged your body. You tightened around him as he drove into you and he growled. 

“Do that again,” he demanded, and all you could do was moan in response. You complied, tensing about his cock and making him groan. 

“God, you’re so needy. Such a little slut. You just love the little trials we’re doing, don’t ya? You dirty fucker. I want you to scream my name so even Gaster can hear you from his studies. I bet you like me watching you when the old skelly fucks you with his little toys, huh? Slut.” All the dirty talk went straight to your heat, and it didn’t help that he kept intermittently flicking your nipples and biting your ear. It took only a few more thrusts for you to feel your heat strain and your climax approaching. 

“Oh, I’m so close..!” You moaned and felt his hands travel from your hips to your face, pressing his smile to your lips. 

“Yell my name, honey, let everyone know who’s fucking you tonight,” he commanded and you had to obey. 

“Please, Sans, keep fucking me, oh Sans - !” You were so close, you thought you were going to explode, until..!

Creeak. 

The door opened and instantly the pressure on and in you left. The light turned on and you could finally see your situation. Sans was gone, to who knows where, and the one who opened the door was..

Gaster.

**Notes for the Chapter:**

> >:3c lmaooooo


	5. Chapter 5

**Summary for the Chapter:**

> Experiment ??: Tentacles, bone popping/teeth, asphyxiation

**Notes for the Chapter:**

> sorry this is kinda late but ive been real busy with the holidays lately! happy holidays! Thanks for reading!

“Where did he go? Where did Sans go? I just heard him, and you! You are supposed to be asleep, but no, my assistant just had to go and mess with the experiment!” Gaster was flustered, walking quickly around the room and having no luck in finding Sans. “He should know better than to do that. And calling me an old man - no respect from him!” 

“Y-you heard.. How much did you hear?” You were trying to hide your naked body from him, blush flushing your face.

“I heard enough, that’s for sure! Screwing with the experiment, how could he? Sometimes I wish I knew what was going on in his h-” You moved just enough to pop your hip, the sound echoing through the room. “...head. What was that.” Gaster gave up in his search for his assistant and turned his full attention to you.

“I-I popped my hip? My joints pop all the time, uh, sorry.” You tried not to move at all to keep it to a minimum, but something in your back cracked instead. Dark grey blush flew to the scientists cheeks. 

“F-fascinating. I-I’ve never.. Can you do it anywhere else?” He brushed his bony hand on your other hip. 

“All over, actually. Keep your hand there, I think I need to pop that one anyway.” You moved your center just right and a loud ‘Pop!’ came from your bones. Gaster could feel the bones moving underneath your flesh, and it made him flinch in surprise.

“M-my! I need to study this more.. B-but this is not the time for another trial.” His face was nearly covered in his blush, and you cracking your ankles and toes didn’t help at all. He ended up taking your ankles in his hands, almost getting angry. “Th-that’s enough! You know what? I know what you and Sans were doing before I was here. You two are quite loud.” He got one knee on the table and lifted himself up onto it between your legs. “I believe he never finished his experiment, did he?” In a quick movement he undid the binds around your wrists. “Why don’t I show you what this ‘old man’ can do.” 

In a flash, black tentacles shot out of his back and surrounded you, replacing the straps and stretching you spread-eagle. He leaned down to you and nearly smashed his teeth to yours, something slimy and large filling your mouth. It explored your mouth, running over each tooth. He pulled back just enough for you to realize it was his tongue. He dove back in and plunged his tongue down your throat, almost making you choke on it. It was a little hard to breathe, but when he moaned, you felt it all the way down your throat. 

One of his hands traveled up to your neck and squeezed lightly, really making you lose your breath. Darkness creeped on the edges of your vision but you were getting more turned on from it. His other hand slipped down between your legs and cupped your heat, making you gasp and buck. He chuckled darkly.

“I’ve wanted to have you to myself since the beginning. But now that I know that my assistant has made quick work of you, I am going to do the same. It’s only fair.” A tentacle sneaked up and poked your hole, sliding in easily as it was coated in slime. You barely got out a moan before it started thrusting hard in you, going farther than anything had ever before. Another one snuck in and eased itself in with the other one, filling you up. The hand around your neck let up and you took a deep breath in, the sudden oxygen going straight to your warmth. You bucked your hips at the feeling of the gooey arms inside of you, wanting more. 

“Please, G-Gaster, i-it’s so much.. m-more, I want mo-ore!” You begged, arching your back as they left you feeling empty for only a second as they pulled out, then filled you up quick and stretched you nicely. He complied, one more tentacle filling you up to the brim. When all three were in you, you lolled your tongue out, the sensation making you see stars. 

“Oh, look at that lewd expression you’re making.. I bet you love my tentacles, don’t you? You love them ramming into you. Let me put that tongue of yours to use.” He took advantage of your open mouth and plunged his own tongue back in, his kisses sloppy. 

With the extra stimulation from his slimy tongue exploring your mouth, you could feel the cord inside of you begin to fray. You moaned against him, trying to let him know. He must have felt the same as he sped up, in and out, the sound of him slapping against your flesh echoing in the room. He hit your spot again and again and finally you released, tightening around him. He groaned and it only took a couple more thrusts for him to come as well, him filling you up with sticky goo. He pulled his tentacles out with a wet ‘Pop!’ and some of the cum came out as well. 

He was nearly panting as he told you, “Well. That was. That was something. I do hope I didn’t hurt you.” His tentacles retracted back into him, leaving him kneeling between your tired legs. “I.. I can see why Sans did this behind my back. Though, I do need to yell at him a little bit for starting without me.” He gave you a coy smile. “Oh, I shouldn’t leave you like this. Hold on.” He finally got off of the table and left, coming back only a moment later with a wet rag and clean pants. 

He cleaned you from both your and his cum, putting your clean pants on you gently once you were clean. He redid the straps on your wrists, but left your legs free. 

“I think I can leave those undone. Give you a bit of a break. Don’t break out now.” He gave you a wink, took away the soiled clothes, and left. The lights shut off after a moment and you sighed happily. An interesting night, to say the least, but you weren’t complaining.

**Notes for the Chapter:**

> i've opened up writing commissions! want a present for yourself or a friend? check out this post to find out more!  
> http://thatssoquailmeat.tumblr.com/post/135809875558/hey-all-soo-im-opening-up-commissions-for-little


	6. Chapter 6

**Summary for the Chapter:**

> Experiment ???: Shower and threesome.

**Notes for the Chapter:**

> guess whos back (back, back)  
> back again (gain, gain)  
> littlequails back (back, back)  
> tell a friend
> 
> i wrote almost 2000 words for you guys as a way of saying sorry!! i have another chapter's plot written out, i just need to fully write it yet. it's coming soon though!! thanks for all the comments and kudos, i never thought id write something that got almost 10,000 hits!!!

You had been strapped down to the metal table for nearly two weeks now. Everything was starting to become pretty gross from your constant lying on it. Sure, you had gotten up a few times to go to the bathroom when a technician was in your room, but nothing had been cleaned during that time. It wasn’t until Gaster and Sans returned that you mentioned something.

“Of course we can get you cleaned up! Our results from your samples have been coming out.. Not as we had planned. Maybe this is why,” Gaster explained as he undid the wrist restraints that held you down. Once freed, you rubbed your wrists and jumped down, stretching out your legs. As you weren’t using them as often, they had become weak, and you leaned on the table for a bit to regain your balance. 

As soon as you were ready, the two skeletons walked you from your room to a separate one a little ways down the hall. Inside you found a large shower with no curtain and a couple unopened bottles inside of it. You stepped all the way inside the room and the scientists followed. Sans closed the door behind them. 

“You.. Are you going to stay while I shower?” you asked. 

“We don’t wantcha getting into anything you shouldn’t, doll. Plus we’d rather not leave ya alone from your room, yknow?” Sans grinned lazily, leaning against the wall. 

Gaster gestured to all of you. “And, we haven’t seen how your joints and muscles interact and move yet. It would be interesting to see how you move naturally. We’d like to feel your muscles as well, so we’ll be cleaning you.” With that, he took the bottles out of the shower, as if to give you no other choice. 

You undress, setting your clothes in a neat little pile by the door. You step into the shower, turning on the water, letting it warm up. As you wait, Gaster and Sans have a heated whisper argument. 

“I told you not to mess with the subject after hours! That could be the reason behind our samples not showing the amount of determination we had seen at the beginning. I blame you for it.” 

“Gast, relax, I was just having some fun. And you’d be lying if you said you didn’t have some fun too. If you blame me, you have to blame yourself as well.” Gaster’s face lit up with blush. “Listen, I think I have a hypothesis as to why the level of determination is lower, but it’s something I’ll discuss with you later. Right now, we’ve got something else,” his eyes motion over to you and back, “to deal with, alright? I’ll get the muscles and write down their movements later, my memory is better than yours.” With that they broke apart and finally noticed you had gotten in the shower. 

Steam rose up to the ceiling quickly, the warmth from the shower doing good on your tight muscles. You rinsed out your hair, sighing in contentment. The skeletons got closer to you, Sans opening the bottle of soap and pouring some in his boney hand. 

“I’m gonna wash you up, Gast is gonna get your hair. We got this stuff from the trash, so uh, we hope it’s still good.” Gaster hit Sans on the back of his head, whispering angrily, “Don’t tell them that, it’s disgusting!” You simply laughed and shrugged your shoulders. From what you could smell of the soap, it was a fresh cucumber and that was definitely alright with you. 

Sans started on your arms, massaging your limb to get a feel for your muscles. Forearm, bicep, tricep, it all got soap and a good rub down. Then he moved to your chest, for once having a sense of decency around him and, for the most part, ignoring your breasts. ‘He’s had enough experience with those anyway,’ you thought. 

Gaster was busy dumping shampoo on your head unceremoniously before threading his fingers through your hair, kneading in the cleaning product. The cucumber smell now wafted through the entire room and you sighed once more, relaxing into the capable bones of the scientists. 

It wasn’t long until Sans reached your legs, paying attention to the large muscles that made up your thighs, then your calfs, and finally the intricate structure that made up your feet. Once both sides were sudsy with soap, he traveled back up to your hips. He rinsed off one hand in the water before giving a wink to his superior and slipping his index finger between your wet folds. You let out a low moan, his thumb rubbing over your clit, which was quickly on its way to becoming swollen. 

Gaster hears your sounds and flushes, suddenly aware of what his partner was doing. He knows that he had been shown up last time that Sans had started without him; this would be different. One of his hands stays in your hair, the other one slides down your arm and finds its way to your breast. He twists a nipple, eliciting a whine from you, and a look of almost pride from Sans. His old boss was catching on, he thought. 

The smaller skeleton decides he wants to get closer to you. He withdraws his hand and backs away from the shower a bit. The two scientists had been simply standing outside of the water as they washed you, so as not to get wet. Sans strips of his lab coat, then sweatshirt, then the rest of his clothing. Once those were thrown across the small room, he stepped into the steaming shower, arching his back in contentment with the heat. Another heat was calling him, however, and he kneeled in front of you. Though his grin was transfixed on his face, he made a tongue appear right between his teeth and licked your clit, drawing out a high-pitched sound from you. 

Gaster, getting more turned on from your little sounds, didn’t want to be outdone. He undressed himself as well, being kinder to his clothes and folding them before putting them on the ground. He slid into the shower behind you, pressing himself up against your back. One of his hands rests on your shoulder, the other one messes with your chest. Once your mouth was open in a groan, Gaster took advantage and kissed you deeply, his tongue interacting with yours. 

The three of you stayed like that, Sans licking and slipping his tongue inside of you, Gaster pinching your nipples and making sure you could barely breath, you being so exhilarated that you think your knees were going to collapse from under you, for nearly ten minutes. Sans notices your knees shaking and motions to Gaster to come down closer to him. They whisper intently, then back away from you all together. Sans chuckles as the room began to grow darker. 

“You’re gonna like this, toots.” 

Black tentacles shot out from behind you, enveloping you and moving you to lay on your stomach on something solid in the shower - you realized it was more tentacles. They were squirming around you and rotating you to be in the perfect position for the skeletons plan. The warm water was hitting your back, your legs were dangling off of this, ‘tentacle table’, and you were face-to-face with.. Gaster’s tentacle cock. You felt Sans’s dick bump up against your backside and he leaned over you, his warm breath tickling your ear. 

“We’re gonna spitroast ya, kid.” 

With that, he slid his cock over your folds, poked in his tip, then rammed the rest of it in. His force made you gasp, and with your mouth open, Gaster slid in his own tentadick. Their thrusts were alternating, leaving one hole filled while the other was left wanting more. You moaned and whine around Gaster’s cock, making him groan as well. 

Gaster couldn’t stay quiet for long. “It’s- it’s interesting to see how, grh, how your back muscles move with our motions, hh, and how-” 

“Gaster, shut up and enjoy this, we’ll think about science later,” Sans interrupted. You almost let out a laugh, if you mouth wasn’t filled up. 

The water seemed to be heating up, or was it you? It felt like each drop was burning your back, turning you on even more. It was too much, you couldn’t take much more. When Gaster’s cock was out of your mouth for a second, you lifted your head up to speak. 

“I-I can’t, I’m go-gonna c-cum, please, please let me c-cum!!” You yelped, stars appearing behind your eyes. Sans never stopped, and although Gaster let up for a second to watch you with a scientific curiosity in his eyes, once you were done with your orgasm, he too began again. 

The overstimulation had you choking around one cock and tightening around the other, your next orgasm coming up much faster. You could tell the scientists were getting close as well, as they started thrusting faster, and in sync this time. You were being used in the best way, being filled up to the brim, then emptied, rinse and repeat. Sans could feel that you were getting close, and instead of continuing to ram into you, started making his cock bigger. It filled you up and stretched you beyond what you thought you were capable of. With the added sensation of Gaster’s tentacle sliding in and out of you mouth, you were close, so close. So close that you didn’t have a chance to let them know, and before you knew it, you were nearly screaming in pleasure, the dopamine in your rushing all around your body, making you feel better than you’d ever felt. Sans came next, his cock shrinking as he filled you up with his cum instead. Gaster was the last one, but made you nearly choke as he thrusted into your mouth and made you swallow mouthful after mouthful of his black cum. 

They were all exhausted. You slumped on the table made of tentacles and Sans laid on top of you. One of Gaster’s tentacles turned off the water, making everyone’s panted breaths echo in the now quiet shower. The taller skeleton couldn’t do much with the smaller one nearly asleep on top of you, so he slapped the back of his skull and he jolted up. 

“Sorry, sorry, the warmth was making me tired.” He chuckled at his own double entendre and got out of the shower, helping you stand up get out of the wet shower safely. Gaster dissipated his extra tentacles except for one, which grabbed towels for everyone. Sans and Gaster toweled off their bones fairly fast, as they didn’t catch much water. You, on the other hand, started by drying off your hair, then toweling off the rest of you and leaving the towel around your waist. 

The three of you made your way back to your room. Gaster decided to forgo the binds this time around. 

“We’re fairly certain that there’s nothing terrible you could get into. However, we would like to warn you that trying to escape will lead to consequences.” Gaster dipped out of the room for a second, then returned with a pillow. “I am very sorry that we didn’t provide one of these sooner.” He turned to the other scientist. “Sans, you remember all of the subjects muscles, yes? We need to write them all down.” His attention was back to you. “We’ll be back when we need more information.” 

Sans winked at you and put his hands in his pockets. “Thanks for a clean shower, toots. See ya later.”

With that, they left and locked the door behind them, leaving you alone. You sighed. This place was certainly becoming interesting, though not in the way you had initially thought.

**Notes for the Chapter:**

> sorry if this is a little off?? i feel like i didnt write gaster as i did before. its been a while since ive written anything though, so sorry!!! thanks for reading!


End file.
